As one of the most common valves used for isolating sections of water systems, knowing what a задвижка is used for can come in handy whether you work in utility distribution or just want to understand your home plumbing better.
In this comprehensive guide, I’ll cover everything you need to know about gate valves including:
- Что такое задвижка?
- The pros and cons of using gate valves
- Examples of gate valve applications
- FAQs on gate valve uses
Let’s start with the basics.
Что такое задвижка?
To understand what gate valves are used for, you first need to understand what they are.
A gate valve is a linear isolation valve designed to start and stop fluid flow through a pipeline. Constructed of a valve body, seat, disc, spindle, and wheel operator, gate valves work by lifting or lowering a gate into the path of flowing liquid.
Sometimes referred to as stop valves or sluice valves, gate valves are operated through clockwise rotation to close or open. They can be actuated manually, pneumatically, electrically, or hydraulically.
The main advantage gate valves provide is an unobstructed flowpath and minimal pressure loss when fully open. This allows cleaning pigs to pass and makes them well-suited for pipelines transporting liquids with suspended solids.
However, because of their multiturn operation, gate valves are slower to operate than quarter-turn valves. As such, gate valves should only be used in fully open or closed positions.
The Pros and Cons of Using Gate Valves
Now that you know the basics of what a gate valve is, let’s go over the key advantages and disadvantages of using them:
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- Full bore design: When open, gate valves provide an unobstructed flowpath, resulting in very little pressure loss. This allows easy passage of cleaning pigs.
- Tight shutoff: The mating of the gate and seats provides leak-tight closure, making gate valves suitable for isolation service.
- Slow operation: The multiturn action of gate valves slowly starts and stops flow, helping to prevent water hammer damage.
- Affordability: Simple in construction and operation, gate valves are an economical valve choice.
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- Slow operation: While helpful for water hammer protection, the multiple turns to open/close gate valves make them poor choices for frequent operation.
- Not for throttling: The flowpath shape of gate valves causes flow velocity fluctuations and vibration if used to regulate flow. This can damage parts.
- Frequent maintenance: Gate valves are more prone to seat wear and disc binding than other isolation valves. Expect to repair/replace fairly often.
As with most valve types, there are always tradeoffs to consider when selecting gate valves. Choosing gate valves comes down to your specific needs and operating conditions.
Применение и использование задвижек
Thanks to their benefits and drawbacks, gate valves lend themselves well to certain applications:
Isolation Service
One of the most common gate valve applications is isolation service. During maintenance, repair, or installation work, sections of water systems need to be blocked in without flow.
Gate valves positioned throughout water distribution networks allow shutting off branches, meters, equipment and other components while maintaining supply through mains. Their low leakage rates allow confidence in isolation during servicing.
Particularly useful in this application are resilient wedge gate valves, offering bubble-tight shutoff around solids that could lodge between the gate and seat.
District Metering Zones
Related to isolation capabilities, gate valves enable creating district metering zones (DMZ) throughout water distribution systems.
DMZs allow monitoring of flow and pressure changes to detect leaks and bursts within a limited area. Gate valves make adjusting boundaries quick, allowing better leak survey accuracy.
Thermal Relief
Gate valves are also useful for thermal relief of pipelines and equipment exposed to rapid temperature changes. Their slower opening helps limit thermal shock.
One example would be drain valves on equipment used for handling steam. Slowly cracking open gate valves limits drastic temperature changes to metal parts.
Slurry Flow
Another of the most common gate valve applications is for flowing slurries. Their full bore shape prevents clogging while allowing passage of solids.
Gate valves are often specified on pipelines in mining, wastewater treatment, food processing, pulp & paper production, and other slurry handling processes. Particularly effective in these services are flexure gate valves.
FAQs on Gate Valve Uses
Let’s wrap things up with answers to some frequently asked questions about what gate valves are used for:
Are gate valves good for throttling?
No. Gate valves should not be used for throttling or flow regulation. Their fluid passageway shape creates turbulence and vibration that can damage parts. Needle, globe, butterfly, and other rotary control valves are better for throttling services.
Can gate valves be operated partially open?
It’s not recommended. Partially opening gate valves increases wear and potential failure over time. For optimal service life, gate valves should only be operated fully open or closed.
What is the main purpose of a gate valve?
The primary use of gate valves is for isolation – starting and stopping flow. Their tight shutoff and full bore design specifically suits them for blocking in sections of pipe networks.
Why choose gate valves over ball valves?
Gate valves are chosen over ball valves when an economical solution allowing full, unobstructed flow is needed. Ball valves generally cost more and have slightly higher pressure drops than full port gate valves.
Additionally, gate valves better withstand water hammer effects thanks to slower operation. However, ball valves allow faster on/off cycling.
Hopefully this guide gave you a comprehensive overview answering the question “What is a gate valve used for?”. Let me know in the comments if you have any other gate valve applications to add!
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